The causes of World War II were rooted in the peace settlement at Versailles in 1919-1920. The peace had created as many problems as it had solved. The senior Allied heads of state yielded to demands that involved annexing German territory and creating new states out of the eastern European empires. In doing so, the peacemakers created fresh bitterness and conflict. The Versailles treaty and its champions, such as US President Woodrow Wilson, proclaimed the principle of self-determination for the peoples of eastern and southern Europe. Yet the new states created by the treaty crossed ethnic boundaries, involved political compromises, and frustrated many of the expectations they had raised. The unsteady new boundaries would be redrawn by force in the 1930s. The Allied powers also kept up the naval blockade against Germany after the end of World War I. This forced the new German government to accept harsh terms that deprived Germany of its political power in Europe. The blockade and its consequences created grievances that made the German people feel angry and completely humiliated.